Chillers operation energy efficiency is the main factors affecting the efficiency of air conditioning systems. A chillers operation energy efficiency model and its method for a real chiller plant were proposed in this paper, whose parameters were optimized by GA optimization algorithm. Moreover, as R_RMSE (Relative Root Mean Square Error) was adopted as the evaluation of the prediction accuracy, the results showed that the prediction accuracy of SVR model based on GA optimization algorithm was better than other models, which average R_RMSE was 4.52%. The method proposed in this paper can predict the operation energy efficiency of the chiller accurately to provide basic for chiller energy efficiency analysis, fault detection and diagnosis, and optimizing control.